The problem seems partially solved.
Now I can enter everywhere, but my problems sending stickies over the local area network (Stickies is a program) or sending Ditto clips continues (Ditto is other program for organizing clips and send clips to other terminals in the local area network)
My solution was :
Suppose that I have changed something in the past. By example the password of the administrator user in the portatil. And therefore have problems by that reason. (I only have password in the portatil because I need to use Cobian Backup in that terminal with the net)
As I continue without enter in the conflictive folders and don't see the security tab, observ 0 bytes in those folders (and have other folders and files with no 0 bytes at all.....) and received denegated access invoking administrator privileges i decided (i never have made changes in the privileges.....):
Enter in secure mode with net access.
The system asked me for the user and password when I try to enter in the first folder of other terminal.
I alway propose my name : JOSE, but the system propose me the terminal name\JOSE. By example Acer-a04555092b\JOSE
Then the password, and click remember, and enter. In this way I could enter in the inaccesible folders.
For me the sympthon is that the asked user is the corresponding to the terminal where the target folder is, not simply the user in the terminal in use : JOSE. (This is was the all system need to know to solve the question......and why affects only some folders seems a bug of windows xp pro.....)
I have recovered partially the traffic originated by Stickies and Ditto, but the sendind and receiving from the Acer portatil continues failing.
I will try in the stickies forum and the Ditto forum and will inform you about the results.
Additionally perhaps we have to consider that the portatil acer have no internet connection - as you know- in the present moment . ( I have put a post in the ubiquity forum for ask about the possibility of a bullet with loadbalancing and failover services).
The router you recommend me have a high price, but with alfa 2 usb device I can do failover. And I don't know if the bullet have that possibility too......
Best Regards
P.D. The come back way is no possible. If I put off the security tab the problem reappear. Even in secure mode.

secure = safety mode ....